With Sergio Aguero and Gabriel Jesus out injured, Man City boss has revealed that the club could not afford to bring in a new frontman during the summer window.
On the Argentine's injury, Guardiola said: "It depends on the injury. When it is minimum it will be 10-15 days. If it is longer it will be three weeks to a month. I don't know.
"When you are four or five months out (with) knee problems, always you have a risk when you come back.
"We tried to handle it as well as possible, just 50-55 minutes a game, but it was not enough to get fit for the next games. He will be back as soon as possible."
City strengthened their defense with Ake and Ruben Dias in the summer and also brought in a winger in Ferran Torres. The injuries to Aguero and Jesus, however, have raised questions over whether the club should also have tried to sign a striker.
Guardiola then responded by saying: "Maybe. We considered it, we thought about another type of striker but we could not.
"If you decide to buy a striker, it has to be a striker in the league of Gabriel and Sergio, but we cannot afford it. That is the reality.
"We thought, 'OK, Sergio is back' and we didn't expect Gabriel to be injured, but sometimes it happens."
City are set to play Marseille in the Champions League tonight in the Champions League.
Check out our Marseille vs Man City preview